Ethyne-bridged conjugated polymers impact a wide-range of technologies. The efficacy of these species derives not only from their established semiconducting and optical properties but also from the facts that these rigid, rod-like structures are readily processable and manifest high photo and thermal stabilities.
Poly(p-phenyleneethynylene)s (PPEs) define the archetypal examples of ethyne-bridged conjugated polymers. These species have been utilized in organic light-emitting diodes (OLEDs) field-effect transistors (FETs), molecular electronics, nonlinear optical materials, solar energy conversion devices,13-15 and in a variety of sensory applications. Considerable effort has been directed toward the development of synthetic protocols for repeating arene-ethyne structural motifs.
The palladium-catalyzed Sonogashira reaction and acyclic diyne metathesis (ADIMET) are two approaches to PPEs. While the Sonogashira reaction is compatible with polar functional groups and water, it requires both dihaloarene and diethynylarene synthons, and is accordingly susceptible to the introduction of butadiyne defects in the PPE polymer, which defects are estimated to range from 1 to 10% even under the carefully controlled reaction conditions.
An ADIMET-based synthesis may circumvent butadiyne defect sites, but this method is generally incompatible with sensitive functional groups that include water-soluble side chains; furthermore, the syntheses of carbyne precursors for ADIMET protocols require inert reaction conditions and cannot be implemented in the presence of water.
Despite the fact that water-soluble PPEs have attracted increasing interest in biosensing and bioconjugation applications, relatively few such materials have been reported.
Accordingly, there is a need for an environmentally benign synthetic approach for PPE synthesis, separation, and purification in neat water under an aerobic atmosphere.